Optical signal processing device

Abstract

An optical signal processing device includes a waveform width widening unit configured to widen a waveform width of an optical signal; and an optical limiter circuit, to which the optical signal the waveform width of which is widened is input, configured to suppress an intensity of the optical signal in a region where an input intensity and an output intensity are not proportional.

1. An optical signal processing device, comprising:
 a waveform width widening unit configured to widen a waveform width of an optical signal; 
 an optical limiter circuit, to which the optical signal the waveform width of which is widened is input, configured to suppress an intensity of the optical signal in a region where an input intensity and an output intensity are not proportional; and 
 an optical circuit, 
 wherein the waveform width widening unit is further configured to adjust an ON level time period and a zero level time period by extending a time period in which the optical signal is at the ON level and by shortening the time period in which the optical signal is at the zero level, 
 the optical limiter circuit is further configured to suppress the noise on the ON level of the optical signal output from the waveform width widening unit, and 
 the optical circuit is configured to change the ratio of the ON level time period and the zero level time period of an optical signal output from the optical limiter circuit back into an original ratio of the ON level time period and the zero level time period of the optical signal. 
 
     
     
       2. The optical signal processing device according to  claim 1 , wherein
 the waveform width widening unit is an optical fiber. 
 
     
     
       3. The optical signal processing device according to  claim 1 , wherein
 the waveform width widening unit is a chromatic dispersion medium or a polarization mode dispersion medium. 
 
     
     
       4. The optical signal processing device according to  claim 1 , wherein
 the waveform width widening unit is a dispersion generator. 
 
     
     
       5. The optical signal processing device according to  claim 1 , further comprising
 a control unit configured to control the waveform width widening unit on the basis of quality of an optical signal output from the optical limiter circuit. 
 
     
     
       6. The optical signal processing device according to  claim 1 , further comprising
 a recovery unit configured to restore a waveform width of an optical signal output from the optical limiter circuit to a waveform width before the optical signal is input to the waveform width widening unit. 
 
     
     
       7. The optical signal processing device according to  claim 1 , further comprising
 a dispersion compensation unit configured to compensate for dispersion of an optical signal output from the optical limiter circuit. 
 
     
     
       8. The optical signal processing device according to  claim 7 , wherein
 the dispersion compensation unit compensates for dispersion provided by the waveform width widening unit. 
 
     
     
       9. The optical signal processing device according to  claim 7 , wherein
 the dispersion compensation unit is an optical fiber. 
 
     
     
       10. The optical signal processing device according to  claim 1 , wherein
 the optical limiter circuit is an optical amplifier having a gain saturation region, and suppresses an intensity of the optical signal in the gain saturation region. 
 
     
     
       11. The optical signal processing device according to  claim 1 , wherein
 the optical limiter circuit is an optical parametric amplifier using a third-order nonlinear optical effect or a second-order nonlinear optical effect. 
 
     
     
       12. The optical signal processing device according to  claim 1 , further comprising
 a power controller configured to control power of an optical signal output from the waveform width widening unit, wherein: 
 the optical limiter circuit comprises a nonlinear optical medium, to which pumping light is input, and operates as an optical amplifier; and 
 the power controller controls the power of the optical signal and the pumping light so that a gain is saturated in the nonlinear optical medium. 
 
     
     
       13. The optical signal processing device according to  claim 1 , further comprising
 a power controller configured to control power of control light input to the optical limiter circuit, wherein: 
 the optical limiter circuit comprises a nonlinear optical medium, to which pumping light is input, and operates as an optical amplifier; and 
 the power controller controls the power of the control light so that a gain is saturated in the nonlinear optical medium. 
 
     
     
       14. The optical signal processing device according to  claim 1 , wherein
 the optical signal is a wavelength-division multiplexed optical signal obtained by multiplexing a plurality of different wavelengths. 
 
     
     
       15. An optical transmission system having a repeater station on an optical transmission line between a transmitting station and a receiving station, wherein
 the repeater station comprises an optical signal processing device, 
 the optical signal processing device comprises: 
 a waveform width widening unit configured to widen a waveform width of an optical signal; and 
 an optical limiter circuit, to which the optical signal the waveform width of which is widened is input, configured to suppress an intensity of the optical signal in a region where an input intensity and an output intensity are not proportional; and 
 the receiving station comprises a dispersion compensation unit to compensate for dispersion occurring in the optical transmission line and the repeater station, 
 wherein the waveform width widening unit is further configured to adjust an ON level time period and a zero level time period by extending a time period in which the optical signal is at the ON level and by shortening the time period in which the optical signal is at the zero level, 
 the optical limiter circuit is further configured to suppress the noise on the ON level of the optical signal output from the waveform width widening unit, and 
 the dispersion compensation unit is configured to change the ratio of the ON level time period and the zero level time period of an optical signal output from the optical limiter circuit back into an original ratio of the ON level time period and the zero level time period of the optical signal. 
 
     
     
       16. An optical transmission system having a transmitting station, a receiving station, and an optical transmission line between the transmitting station and the receiving station, wherein:
 the receiving station comprises: 
 an optical signal processing device; and 
 a dispersion compensation unit to compensate for dispersion occurring in the optical transmission line, 
 the optical signal processing device comprises: 
 a waveform width widening unit configured to widen a waveform width of an optical signal; and 
 an optical limiter circuit, to which the optical signal the waveform width of which is widened is input, configured to suppress an intensity of the optical signal in a region where an input intensity and an output intensity are not proportional, 
 wherein the waveform width widening unit is further configured to adjust an ON level time period and a zero level time period by extending a time period in which the optical signal is at the ON level and by shortening the time period in which the optical signal is at the zero level, 
 the optical limiter circuit is further configured to suppress the noise on the ON level of the optical signal output from the waveform width widening unit, and 
 the dispersion compensation unit is configured to change the ratio of the ON level time period and the zero level time period of an optical signal output from the optical limiter circuit back into an original ratio of the ON level time period and the zero level time period of the optical signal.